Renzi's Democratic Party won 40.8 percent of the Italian vote for European Parliament, fortifying Renzi's push to overhaul Italy's economy and bureaucracy. The Democratic Party's tally was nearly twice the 21 percent garnered by its nearest rival, the anti-euro 5-Star Movement, and also far above Silvio Berlusconi's Forza Italia, which won 16.8 percent.

"The result tells us the change we promised needs to come even more quickly than we imagined," Renzi told a news conference in Rome. "In what had become a head-to-head battle between anger and hope, Italians chose to give hope twice the votes of anger."

Renzi had campaigned for reforming Europe from within during a heated campaign against populist, Europe-skeptical parties: former comic Beppe Grillo's 5-Star Movement and the Northern League. His party had the strongest showing of any in Europe, and put Italy alongside Germany in a pro-Europe camp after the French far-right won a record victory. Milan's stock exchange soared 3 percent at Italy's vote of confidence in Europe.

Renzi declared "this is Italy's moment," as the euro-zone's third-largest economy prepares to take over the rotating EU presidency on July 1.

The Democratic Party had the best showing ever for a center-left party in Italy, while Berlusconi, constricted by a tax fraud conviction, suffered his worst result ever.

Grillo, whose movement was the top vote-getter in 2013 political elections, told his followers not to be discouraged — but was clearly chastened. "We will be even a stronger opposition and try to stop the bleeding of this country," he said.